1. Field of the Invention
The present invention relates to a beveling wheel, method for forming a beveled lens with the beveling wheel for use with eyeglasses, and a beveled lens.
2. Background Art
Reliable assembly of eyeglasses is crucial to the many wearers of prescription, safety, and/or sun glasses. It is unfortunate that lenses often fall out of eyeglass frames after a period of wearing. In some cases, this is the result of shrinkage and/or creep of a plastic material when used for the lens. Often, an opportunity for falling out is aggravated by the relative thinness of the cross-section of the eyeglass frame, such as an eye-wire frame or a frame only having a partial frame holding for retaining the lens.
Another failure mode occurs when the glass lenses crack as a result of having an interference fit of the vertex of the bevel with a bottom of a channel portion of the eyeglass frame. It is well practiced in the art to avoid cracking of the lens by having the bevel vertex not in contact with the bottom of the channel of the eyeglass frame. As such, glass lenses have always been manufactured to have bevels which will not contact the bottom of the eyeglasses frame.
Diamond beveling wheels are customarily made for use of lens edging equipment that edges the lenses to fit into eyeglass frames. These diamond beveling wheels use technology intended to form the bevel shape required for lenses made of glass. But, today 94% of all eyeglasses are made from plastic lenses using lens edging machines designed to edge plastic lens material.
It is an unfortunate consequence of using beveling wheels designed glass to edge plastic lens materials that the bevel is not fully inserted into the channel of the eyeglass frame. When the plastic lens is not fully inserted, the lens is prevented from forming an optimal interference fit between the lens and the eyeglass frame. As a result, a plastic lens is very susceptible to falling out of the eyeglass frame caused by shrinkage of the lens, loosening of the retention screws or twisting of the frames.
What is needed is a lens that can be assembled into many types of eyeglass frames to yield a more secure assembly of the eyeglass lens and frame that decreases the possibility of the lens falling out.
What is further needed is a beveling wheel which can manufacture a bevel on the lens that can overcome, at least to some degree, the issues of shrinkage, stress and cracking of the lenses.